We have shown the blood pressure is significantly elevated in the young of one of two normotensive rat strains suckled to spontaneously hypertensive (SH) mothers. The goal of the present research is to better define the extent of the maternal influence on blood pressure development in offspring and elucidate the mechanism of maternal transmission of high blood pressure to the young. The relative effects of intra-uterine exposure of they embryo and the suckling of the pup on blood pressure development of normotensive and hypertensive rat strains will be studied by embryo cross-transplantation and pup cross-suckling techniques. The blood pressure of the offspring will be monitored well into adulthood, providing information of the nature of the response with regard to interval of development, duration, severity, and reversibility. In addition, we will examine the hypothesis that the elevation in blood pressure observed reflects the action of two opposing mechanisms, the pressor effect of a circulating hypertensinogen versus the resistance to the influence of the compound. Purified extracts of tissue from SH rats will be prepared for characterization of the acute effects on vascular sensitivity to norepinephrine and the subacute and chronic effects on resting blood pressure. The subacute and chronic effects of standard doses of the preparation will be subsequently studied in truly normotensive Sprague-Dawley, labile Wistar-Kyoto, and spontaneously hypertensive rat strains. The data obtained will give insight into the mechanism promoting blood pressure elevation in the spontaneously hypertensive rat model as well as indicating the significance of individual and between strain differences in resistance to hypertensive blood pressure elevation.